The First Introduction of an Exogenous 5′ Untranslated Region for Control of Plastid Transgene Expression in Chlamydomonas reinhardtii

The utilization of heterologous 5' untranslated regions (5 ' UTRs) for expressing foreign proteins in the chloroplast of Chlamydomonas reinhardtii (C. reinhardtii) has posed a persistent challenge over the years. This challenge stems from the lack of a defined and comprehensive set of translational cis-elements responsible for stability, ribosome binding, and translation initiation, which are mediated by trans-acting factors native to C. reinhardtii. In the current study, we aimed to address this bottleneck by employing the 5 ' UTR from gene 10 of the T7 bacteriophage (T7g10 5'UTR), fused to the promoter of C. reinhardtii small subunit ribosomal RNA (rrnS), to facilitate the translation of a reporter gene, YFP. Using a chimeric construct, the YFP mRNA was efficiently translated utilizing the heterologous T7g10 5 ' UTR. Furthermore, the accumulation of YFP protein under the control of the T7g10 5 ' UTR was approximately one third of that observed under the control of the endogenous psaA promoter/5 ' UTR in the C. reinhardtii chloroplast. The results of computational analyses demonstrated that the T7g10 5 ' UTR sequence shares common elements with the endogenous 5 ' UTRs of the chloroplast genes. Moreover, the findings of the current study highlighted the potential of employing bacteriophage 5 ' UTRs for the foreign protein accumulation from the chloroplast genome of C. reinhardtii. [GRAPHICS] .